Variation of Hubble constant in cosmological time

Click For Summary
SUMMARY

The Hubble constant is confirmed to decrease over cosmological timescales, with its value tending towards infinity in the early universe due to the relationship H=V/D, where H is the Hubble constant, V is the recessional velocity, and D is the distance. During the radiation-dominated epoch, the relation H = 1.67 √(g_{*}) (T²/M_{P}) holds true, but it does not apply during the inflationary epoch. The behavior of the Hubble parameter during inflation depends on the equation of state of the inflation-driving component, potentially remaining constant if it behaves like a cosmological constant. For further insights, a review article is available at this link.

PREREQUISITES
  • Understanding of the Hubble constant and its significance in cosmology
  • Familiarity with the concepts of recessional velocity and distance in an expanding universe
  • Knowledge of the radiation-dominated and inflationary epochs in cosmological history
  • Basic grasp of equations of state in cosmology
NEXT STEPS
  • Research the implications of the Hubble constant on cosmic expansion
  • Study the dynamics of the radiation-dominated epoch in cosmology
  • Explore the role of the equation of state in the inflationary epoch
  • Examine the relationship between dark energy and the Hubble parameter
USEFUL FOR

Astronomers, cosmologists, and physics students interested in the evolution of the universe and the implications of the Hubble constant on cosmic dynamics will benefit from this discussion.

spaghetti3451
Messages
1,311
Reaction score
31
Is the Hubble constant decreasing over cosmological timescales?
 
Space news on Phys.org
Yes:
H evolution.png
 
Why did the Hubble constant tend to infinity in the early universe?
 
Mostly for the same reason that f(x)=1/x goes to infinity as x goes to 0. Remember that H is the proportionality factor between recessional velocities and distances: H=V/D. As the distances between receding objects decrease to 0, H goes to infinity.
An additional effect comes from V being larger in the past, but that's secondary.
 
  • Like
Likes   Reactions: spaghetti3451
The relation

$$H = 1.67 \sqrt{g_{*}} \frac{T^{2}}{M_{P}}$$

is valid during the radiation-dominated epoch. Is it valid during the inflationary epoch?
 
spaghetti3451 said:
The relation

$$H = 1.67 \sqrt{g_{*}} \frac{T^{2}}{M_{P}}$$

is valid during the radiation-dominated epoch. Is it valid during the inflationary epoch?
No.
 
  • Like
Likes   Reactions: spaghetti3451
What would be the correct relation for the Hubble parameter in the inflationary epoch?
 
That would depend on the equation of state for whatever is driving inflation. If what drives inflation behaves as a cosmological constant, then the Hubble parameter would be constant during inflation.
 
  • Like
Likes   Reactions: spaghetti3451
Would you share a review article which discusses this in more detail?
 

Similar threads

Undergrad Hubble Constant, Dark Energy and the Expanding Universe
  • · Replies 15 ·
Replies
15
Views
4K
Undergrad Age of the Universe and the Cosmological Constant
  • · Replies 17 ·
Replies
17
Views
2K
Graduate Updated Hubble constant from TRGB measurements
  • · Replies 4 ·
Replies
4
Views
2K
High School Which statement is more accurate? (Hubble's redshift vs. Hubble's law)
  • · Replies 13 ·
Replies
13
Views
2K
Undergrad Question about the Hubble Constant
  • · Replies 14 ·
Replies
14
Views
2K
High School History of Cosmology: 1915-1929 | Einstein, Hubble & GR
  • · Replies 19 ·
Replies
19
Views
3K
High School The distance to the nearest identical Hubble volume in light years?
  • · Replies 50 ·
2
Replies
50
Views
7K
Undergrad Latest Findings from DESI Collaboration
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad How to calculate the mass within the Hubble Sphere?
  • · Replies 3 ·
Replies
3
Views
1K
Undergrad Has JWST solved the crisis in cosmology?
  • · Replies 2 ·
Replies
2
Views
3K